I'm currently running CS5 ID and PS in a Parallels 14 macOS Sierra VM along with another critical app that stopped working in High Sierra. Runs fine on my iMac. Just create the VM using a USB drive containing the Sierra install app, then restore your new virtual HD from a Time Machine backup. No need to install the apps again.

Tried to open APub and got the Update to 192 notification. However, all clicks resulted in an error sound with everything locked. Could not even quit and had to do a Force Quit. Tried multiple times with same results. It had worked for me with a couple previous updates, so not sure what went wrong with this one.
High Sierra

As a side note to using CS5-6 ID and PS with macOS changes, it had held us back from upgrading to High Sierra. However, after some work and research, I upgraded my Parallels and added a Sierra Guest VM where my CS5 apps run just fine. After upgrading to High Sierra on the real HD, I find that my CS 5 apps work there fine as well, so still very usable. However, I'm going to keep my virtual Sierra drive for a couple other apps that died with the High Sierra upgrade. They all are running just fine in the virtual drive and I have copy/paste, file sharing between the real HD (High Sierra) and the VM, so it's providing a great workaround to keep my legacy apps working.
On getting ID files into APub, as I've said in previous posts to this thread, it is critical to be able to do this. Our company has massive client files in ID and PS that have to be able to be used as the basis for revisions, etc. While I have used the Open PDF in APub, as stated by many, that method has a lot of limitations that make it only appropriate for small, simple file conversions. Anything complex, it simply won't import correctly. That means a huge cost to the client to rebuild the entire document in APub, something most clients simply won't pay. If APub is going to become part of the workflow, we really need to be able to use our legacy client files.
When we switched to APhoto from PS, we had reasonable success in importing most (but not all) PS files, so the transition has been good for the most part (still missing some critical comparable features). But with APub, if we are to actually switch to it, we have to be able to get a majority of our client files into APub. Over the many, many years of doing this (going back to Aldus PM V1), we have never had the need to use IDML, so have no knowledge as to whether that will be a reasonable way to convert our thousands of ID client files. I hope it will work given that Serif has stated that they are working towards adding that. But that is an area where we have no experience. We have numerous complex corporate CS5 ID files that require conversion/import if we are to use APub in our workflow. That's why we're following this thread to see if this is going to turn out well. Love APub so far, but do need the ability to bring in old client files!

As a follow-up (slightly delayed), we recently upgraded to High Sierra plus the newest 157 build. Thus decided to see if the spelling language had been resolved. In High Sierra, we were able to follow your guide for finding the improved Language settings where we could finally turn off the multiple never-used languages. We also had to turn back on British English despite having had it as one of the two "preferred" languages in Sierra. Once that was done and we restarted APub, we are now getting the correct choices of US and UK English. Finally!!! I think the main issue was Sierra versus High Sierra and how Languages are set/available.
Anyway, RESOLVED!

Recently upgraded to High Sierra and both InDesign and PS CS5 work fine. Only quirk is that they both do an unexpected quit after you quit the app (as in Sierra). Everything works fine, everything is saved, but it does throw the dialog. Everyone using it just ignores the notification.
Some people are reporting that CS5 is also working on Mojave, but we're not brave enough to try that yet!
That said, we look forward to migrating to Affinity products in order to enjoy newer technology, better interface, and decent pricing. But like many, we do need to import our massive catalog of client InDesign work since much of what we do is based on previous client work. And in many cases, opening a pdf doesn't bring in things properly for a more complex document (as discussed in numerous threads). But we're hoping that one way or another Affinity will figure this thing out and figure out a way to allow us to do our work using APub. But besides ID importing, we also require web links for our pdf exports since so much "printed" work today is distributed electronically as a pdf, thus requiring web links. But we're again hoping that issue gets resolved as well.

The missing font(s) were Futura variations and a couple Swiss. We tried to replace the Futura with our Futura of the same or other styles. Most (and the correct variations) don't stick (as per the video). The Swiss are now sticking, though didn't previously. I tried with other fonts and some stick while others don't. Again, we may have faulty fonts such as our Futura families, or the pdf may contain faulty futura fonts. Not really sure, although we did get it to happen with a couple other fonts that I can't remember at this moment.
ScreenRecord-Font_Change.mov

Just tried it with 140 and still have issues. Some changes in the missing fonts stick while most do not. Seems I can change the font family but the style seems random as to whether it will stick or not. Not had that issue in ID with these files.
I also just tried opening it in AD and it has the same issue, so perhaps there is something wrong with the pdf, or even possibly with my fonts! However, I've never had this issue with other apps including ID and PS, so not sure what to say.
Aero-Fac A4 6pp Brochure.pdf

Still doing it with 139. Multiple PDF's that are opened in APub do it. I've attached one of them I just tried 139 with. Open Resource Manager, Select all graphics, click on Make Linked, once Open dialog opens, click cancel and APub crashes every time.
Yacht Photo Package Brochure v2 - bleed.pdf

Yes, I can Open a pdf and get most of everything coming through okay. However, I cannot copy/paste any text blocks from ID-CS5 into APub. All text blocks paste as individual lines of text and not in blocks, making it useless since the process to redo all the text in anything but a business card would be too much.
Are you getting the same thing? It's not clear in your post if you are copying/pasting or Opening a PDF.

Just tried this again in the newest beta (133) and does same thing. Opened a PDF of an ID file as a new document, opened the Resource Manager, selected all images, clicked to make linked, then when the Mac Open Dialogue opened up, I clicked Cancel and the app crashes. Did it multiple times.

Tried opening a pdf from ID. It said several fonts were missing. When I tried to select the replacement fonts and styles, the styles refused to stick (selected CondBold and it kept reverting to CondLight). Also refused to accept a selected font for several other instances of a missing font.